Evaluation of a Novel, Large Volume Evaporative Sample Preparation Technique
Mr Felix Massat, Benoît Planel, & Antoine Venezia
Laboratoire départemental d’analyses de la Drôme, Valence, France
Introduction
When introducing any new piece of instrumentation or equipment into a highly
controlled environment such as an environmental analysis laboratory, the new unit must
evaluated to ensure that it has equivalent or better performance to the existing
equipment. Any impact on the testing methods can then be fully understood and the
testing methods re-validated if necessary. With regard to sample concentration and
evaporation technology the most important issue is sample recovery, especially for very
volatile analytes. As part of their evaluation of new equipment Laboratoire
départemental d’analyses de la Drôme (LDA26) evaluated the new Genevac Rocket
evaporation system and its ability to prepare large volume samples containing volatile
analytes. A summary of the data is presented in this report.
Rocket Evaporation System
The Rocket evaporation system is a new parallel
evaporation system which evaporates up to six flasks
each containing up to 400ml in parallel. The system
uses vacuum to evaporate the samples, which spin in a
centrifuge to ensure that there is no sample loss or cross
contamination due to “bumping”. The samples spin in a
low pressure, low temperature steam bath, which
provides precise, even and very high energy heating,
making sample concentration very fast. 1 The Rocket
evaporator has two styles of flask, a traditional bottle
shaped design, and SampleGenie™ style flasks which act
like a funnel and permit the large volume sample to be
concentrated directly to a gas chromatograph (GC)
autosampler vial. Speed an reduction of sample transfer
steps are desirable in a sample preparation method to help
streamline workflow in the laboratory.
Figure 1 – Genevac Rocket
Evaluation of Rocket and Comparison to existing equipment
Samples of the volatile environmental analytes were spiked (50mg/litre) into 100ml of
a 50:50 volume:volume mixture of DCM and acetone. Each sample also had a 50µl
drop of pentanol added as a solvent keep. Samples were evaporated in SampleGenie
style flasks in the Genevac Rocket set at 35°C using the HPLC FRACTION method, to
leave just the drop of pentanol. The Rocket is designed to stop the evaporation
automatically at this point. Following evaporation the samples were made up to 1ml
with a 50:50 volume:volume mixture of water and acetonitrile adjusted to pH 2 and
injected into a gradient HPLC system using a multi wavelength fluorescence detector
(HPLC-Fluor) for analysis. The recoveries are reported in figure 2.
Evaluation of a Novel, Large Volume Evaporative Sample Preparation Technique
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Figure 2 – Percentage recovery of volatile analytes prepared in Genevac Rocket
SD = Standard Deviation
Naphthalene
Methyl 2 naphthalene
Acetonaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Methyl 2 fluoranthene
Benzo a Anthracene
Chrysene
Benzo b Fluoranthene
Benzo k Fluoranthene
Benzo a Pyrene
Dibenzo ah Anthracene
Benzo ghi Perylene
Indeno 123 cd Pyrene
Assay 1
82
92
95
96
104
101
99
103
99
101
100
102
98
104
100
101
101
Assay 2
94
92
94
99
96
96
100
97
102
98
101
104
104
97
100
104
104
Assay 3
92
96
97
105
99
101
101
97
102
100
101
103
103
99
101
100
103
SD
6.43
2.31
1.53
4.58
4.04
2.89
1.00
3.46
1.73
1.53
0.58
1.00
3.21
3.61
0.58
2.08
1.53
By way of comparison these results were compared to earlier work done evaluating
another vacuum evaporation system for multiple small volumes with an alternative
method in use at LDA26, the TurboVap. The samples were of 50ml volume, and
prepared and analysed similarly to those in the Rocket2, results are shown in figure 3.
Figure 3 – Percentage recovery of volatile analytes prepared by two stage evaporation
using different methods, Genevac EZ-2 and TurboVap
Analyte
naphthalene
2 methyl naphthalene
acetonaphthene
fluorene
phenanthrene
anthracene
fluoranthene
pyrene
2 methyl fluoranthene
benzo a anthracene
chrysene
benzo b anthracene
benzo k anthracene
benzo a pyrene
dibenzo ah anthracene
benzo ghi perylene
indeno 123cd pyrene
Genevac EZ-2
Test 1
Test2
75
79
86
87
101
101
100
100
119
120
93
94
103
104
120
121
103
105
92
93
102
102
105
105
121
120
105
105
122
120
107
105
110
110
TurboVap
Test 3
Test 4
28
21
40
35
50
47
51
50
69
61
56
51
74
64
86
76
83
73
80
73
88
81
96
87
110
100
93
82
112
100
96
86
102
91
Evaluation of a Novel, Large Volume Evaporative Sample Preparation Technique
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Conclusions
The new method of evaporation using the Genevac Rocket delivers excellent sample
recoveries and in the case of the most volatile environmental analytes provides
enhanced recovery over the pre-existing methods of evaporation tested. In the Rocket,
vacuum evaporation causes the solvents to boil at a low temperature keeping the
samples at the boiling point of the solvents. By comparison when using the other
methods under test the samples are kept at the elevated temperature of 35°C for the
duration of the evaporation process. This increased temperature of operation will
increase the evaporation rate of both the solvents and the most volatile components in
the sample. By careful control of evaporation conditions in the Rocket, the solvents
can be preferentially removed leaving the analytes and solvent keep behind.
References
1. Lee-Smith, Roger, 2008. Development of a Novel Parallel Evaporator. First
Published in SP2, Vol. 7, No. 39, November, pp 38-39, and also available via
www.Genevac.com/rocketmovie
2. Massat, F, Planel, B & Venezia, A, 2007, Evaluation of Evaporative Sample
Preparation Techniques. First published in International Environmental
Technology, March/April 2008, pp 36, and also available via
http://genevac.org/en/ArticleDetail.asp?S=6&V=1&ProductDownload=134
About the Authors
Mr Felix Massat is head of the Laboratory; Benoît Planel is a Chemist; and
Antoine Venezia is head of Research and Development; all at: Laboratoire
départemental d’analyses de la Drôme, Valence BP118, 26904F-91, France
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